A heart wire or heart wires are typically positioned epicardially to the myocardium and stitched or passed through a myocardial tunnel. Typically, they stay in a patient between one and seven days, usually for one to two days, and preferably less than seven days, after open-heart surgery. Before a patient is released from a hospital, the heart wire or wires are pulled out of the myocardium. Since a myocardium is a moving muscle, a heart wire connected to the myocardium must be able to move. Thus, a heart wire is intended, though only temporarily, to be fixed on a moving muscle. Since the muscle can move, there is a concern that the heart wire can become dislodged. To address the concern for retention of a heart wire in myocardial tissue, heart wires have been designed that have irregular or three-dimensional structures, such as zigzagged and/or tines of prolene material. When these structures are pulled out when no longer needed, the myocardial tissue may be injured or disturbed and there is a risk of bleeding. The risk of bleeding is particularly relevant for patients that may be prescribed blood thinners at the time where the amount of bleeding may be increased.
One effort to reduce bleeding at the myocardium associated with removal of a heart wire is to place a conductive portion of the heart wire under a pledget so that the heart wire is in contact with a surface of the myocardium. Pledgets are relatively small biocompatible cotton, Teflon or similar material that may be stitched to the heart by fine prolene sutures to repair or close the heart. These pledgets are permanently sutured to the myocardium. One technique of placing a heart wire is to place a heart wire with an electrically conductive end under a pledget and suture the pledget to the myocardium. The heart wire has an irregular three-dimensional end (e.g., a hook, zigzag or tines or prolene material) that serves to retain the heart wire under the pledget. When the heart wire is removed, the heart wire including the irregular three-dimensional structured end may be removed without damaging the myocardium.
One concern of placing a conductive portion of a heart wire on a surface of the myocardium is whether the heart wire is placed over adequate (e.g., healthy) tissue, or scar tissue or fat. If the heart wire is placed over scar tissue or fat, there is a risk that attempts to pace the heart through this heart wire will fail.
Typically, when a heart wire is placed in a patient, a physician will put an extra length of wire in the form of a loop inside the patient to increase the freedom of movement of the wire when the myocardium moves (e.g., when the heart is beating). In addition to the risk of injury or disturbance to the myocardium when a heart wire is removed, there is a risk that the loop of wire being pulled out may catch a vein or other structure. This risk is especially dangerous when a loop of wire becomes tangled around a vein graft, which may moreover have metallic clips applied at its branching sites.
One technique to reduce the additional length of a heart wire (e.g., extra looping length) is to connect the heart wire to the pericardium. To expose a heart of a patient, a physician must open the pericardium. Opening the pericardium requires a longitudinal cut therethrough with the sides of the pericardium that have been cut remaining in a relatively fixed position relative to one another. A physician then connects one or more heart wires (e.g., a negative lead and a ground wire). The heart wire or wires may then be connected to the pericardium. Because the pericardium is close to the chest walls of the patient, the need for an extra length or loop of wire is reduced. Another option to reduce the length of additional wire retained in a patient is to use a chest tube. Chest tubes are commonly used to evacuate blood from the mediastinum (interpleural space) after open-heart surgery. They are also used to evacuate air and blood from the thoracic cavity after thoracotomy for lung or pleural surgery. A chest tube typically stays in the mediastinum after heart surgery for one to three days depending on the amount of post-operative drainage present. Following open-heart surgery, chest tubes are typically located very close to the heart and extend out of a patient's chest through the skin and are fixed with a suture in that location. A commonly-used type of chest tube is a plastic tube made of biocompatible synthetic rubber, which is between 20 and 40 centimeters long, and has holes at a distal section. The holes allow excess blood to enter the chest tube. The chest tube is typically connected to a vacuum machine.
In one known design, a heart wire is connected to a chest tube and inserted at the same time as the chest tube. After insertion of the chest tube, the heart wire can be partially disconnected from the chest tube if necessary to reach the myocardium. An advantage of this combination is that when it is time for the chest tube and the heart wire to be removed, they can be removed together. Another advantage is that the heart wire follows a direct path to the heart, so there are no additional loops of wire needed. Thus the risk of a heart wire being tangled on a vein is reduced. In bipolar heart wire configurations, another advantage is that a chest tube can incorporate the ground pole associated with the heart wire leads.